[TowerTalk] Yaesu Rotator Puzzle

[Pete Smith]

I have a G-1000DXA and a G-800SA for the top and bottom tribanders in my 
stack, respectively.  Recently the top rotator (the DXA) started to behave 
erratically.  When I would press the "left" or "right" ends of the control 
bar, the indicator would taker off 45-90 degrees and then begin to indicate 
very slow and somewhat irregular antenna rotation.  I thought I might have 
a connector problem, so I cleaned the connector at my entry panel, to no 
avail.  Then I switched the two controllers, and to my surprise, the 
problem 98 percent cleared up (the G-800 controller on the G-1000 rotator 
still displays a momentary indicator swing of ~5 degrees, before rotating 
and indicating position normally).  The G-1000 controller seems completely 
normal.

I talked to Jerry Darby at Yaesu, who is pretty knowledgeable about the 
rotators, and he said that this was a new one for him.  He did say that the 
circuits of the SA and DXA controllers that senses the antenna's position 
are a little different, so that they might react differently to some sort 
of cable problem - excess capacity to ground, for example.  I'm not sure 
that I can measure that, but I did measure the resistance of the motor 
windings and the rotator pots - the pots seem virtually identical, but the 
G-1000 motor reads 15 ohms, while the G-800's reads 30.  Jerry says that 
the motors are the same, so this may be indicative, but he could not 
suggest what to look at next.

I have a workaround, described above, but suspect that there is still 
something in the cable to the DXA that is haywire.  Does anyone have any 
suggestions for diagnostic steps I can take, hopefully from the ground?

73, Pete N4ZR
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